Method of processing lubricating oil



Patented July 17, i951 UNITED STATES TNT OFFICE METHOD OF PROCESSING LUBRICATING OIL BY TREATING WITH A PHOSPHORUS SUL- FIDE AND THE RESULTING PRODUCTS John D. Bartleson, East Cleveland. Ohio, assignor to The Standard Oil Company, Cleveland, Ohio,

a corporation of Ohio No Drawing. Application May 29, 1948, Serial No. 30,203

22 Claims. (Cl. 25.2-46.6)

This invention relates to processes of improving hydrocarbon base lubricants, and more particularly to the treatment of hydrocarbon lubricants with a small amount of a phosphorus sulfide to form lubricants having improved properrived from natural sources, such as petroleum. For many purposes so-called additives must be included with the hydrocarbon base stock in order to provide a lubricant having particularly desirable characteristics. Generally the inclusion of these additives is associated with a higher cost of the finished lubricant. The preparation of a finished lubricant directly from hydrocarbon base stock by chemical finishing or refining the entire stock at a commercially interesting cost has been a particularly baflling problem to the art.

In accordance with the invention, it has been found'that hydrocarbon lubricating oil stock may be reacted with a small amount of a sulfide of phosphorus, (excluding halogen containing compounds) and the resulting reaction product is an improved lubricant; i. e., a chemically finished or refined lubricant. Such'lubricants are suitable for use under various conditions, including high temperatures or high pressures or both; as, for instance, use in an internal combustion engine operating at high temperatures and in which the lubricant is in close contact with metallic surfaces, metal compounds and high temperature gases. They are also suitable for use in extreme pressure lubricants, e. g., in oils and greases containing the same.

The objects'achieved in accordance with the invention include the provision of a process for chemically refining or finishing hydrocarbon lubricant stock, and the provision of the resulting finished or refined lubricant; and other objects which will be apparent as embodiments or details of the invention are set forth hereinafter.

The reaction of the hydrocarbon base stock with the phosphorus sulfide may be conducted with direct admixture of the reactants, or, if desired, by their admixture in the presence of a diluent which may be subsequently removed. Generally a diluent is not necessary. The reaction is usually complete in about 10 hours or less time, generally 1 to 2 hours. The reaction time is a function of the temperature, the amount of sulfide that is to react, the subdivision of the reactants, the efiiciency of mixing the reactants, and the like.

The hydrocarbon lubricant stock is reacted with the phosphorus sulfide or a mixture of phosphorus sulfides in a ratio of from about 0.1 or somewhat less to about 0.75% by weight, based on the weight of the hydrocarbon lubricating base stock, preferably about 0.3 to 0.6% in the case of P2S5 and 0.15% to 0.4% in the case of P4S3. This unusually small amount is noteworthy in view of the results obtained and the low cost.

Phosphorus pentasulfide is preferred, and since it is most economic and readily available, it is used in most of the illustrative examples. Phosphorus sesquisulfide is used in some of the examples.

The refining of the hydrocarbon lubricating base stock with the phosphorus sulfide may be carried out in the presence or absence of air, or in an atmosphere of inert or non-deleterious gas, such as nitrogen or H28. It may also be carried out under pressure, e. g., pressure generated when the reaction is carried out in a closed vessel.

The refining temperature varies with the hydrocarbon stock. Generally the temperature should be at least 275 F., but should be below the temperature at which the reaction product would be decomposed. A temperature in the range of about 300 to about 450 F. is preferred in many cases. The final refined oil is preferably centrifuged or filtered to remove any by-products, sludge, or other by-product material. If a volatile diluent is used, it may be removed by evaporation. The reaction is uncatalyzed.

The hydrocarbon lubricant stock to which the process is applied may be a raw oil, an acidtreated oil, or a solvent-extracted or refined oil, i. e., oils treated in accordance with conventional modern methods of refining lubricating oils to remove aromatic components. The raw oil may be a fiuid hydrocarbon lubricating base stock having a viscosity at F. of 10 to 500 centistokes such as that used as the base for the 3 SAE to 50 oils. It may be obtained as a distillate from natural or from synthetic material, such as petroleum, and oils produced by cracking, polymerization, hydrogenation, and the like methods. The acid-treated stock may be de- 5 rived by subjecting the above raw hydrocarbon stock to the well-known sulfuric acid refining treatment. This treatment involves both chemical and physical effects. Some of the ingredients in the hydrocarbon stock'may react with the acid '10 to form arsludge, which is separated out. Other ingredients, in the stock are selectively dissolved by the acid, and these are also separated as a sludge. The solvent refining, process is Wellknown, and generally involves'ionly. physical effects. Usually, the solvent selected is furfural, phenol, liquid sulfur dioxide and others known in the art. It dissolves such constituents 'as aro=- matic, unsaturated, and low-"viscosity indexrma terials, and these are separated out. The acid treatment usually removes asphaltic constituents; where necessary, a separate propane or the: like de-asphalting treatment may be used in connection with the solvent refining. Both the'acid or solvent refined oils may be treated with clay before the treatment with the sulfide'to'improve' theircolor, selectively remove impurities; or neutralize the oil. Suchoils are characterized 'in' the industryand'inthis application as'refined oils.

In orderto illustrate andpoint out some of the advantages of the invention, but in no sense as a limitation thereof, the following specific embodiments are included.

In these examples the. following? hydrocarbon lubricant stocks are used.

Raw #300Red Oil (a conventional Mid-Continent lubricating 'oil stock,'of 20-30 S; A. E. vis- 40* cosity) Solvent extractedoil' (a conventional solvent extracted or. refined "Mid-Continent lubricating oil stock) Solventextractedoil, treated with 8-lbs; of clay' per'barrel of oil after extraction (a conventional solvent extracted or'refined and clay treated lubricating oil base stock) fied hereinafter by the example number.

Amount of Hydro- Example Number Phosphorus carbon Sulfide Oil The'following examples are-conducted' simi- 76- F4 larly, except at the following indicated temperatures:

The Sohio corrosion test was used in evaluating lubricants made in accordance with the invention. This test is described in a co-pending applicationof E. C. Hughes, J. D. Bartleson, M. L. Sunday and M-J MT Fink, which also correlates the results of the laboratory tests with a Chevroletengine" test.

Essentially the laboratory test equipment consists 'of -a-vertical thermostatically heated glass test tube-(45 mm. outside diameter and 42 cm. long) into which is placed the corrosion test unit. An air inlet is provided for admitting air into thelower end of the corrosion unit in such a way that in rising the air will cause the oil and suspendedvmaterial.therein' tocirculate into the corrosionnnity The tube is filled with an amount of the oil to'beitested'whichis'at least sufiicient to isubmerge'th'e metals being tested.

The corrosion'test unit essentially consists in a 'circular relatively fine grainedficopper-lead test piece of O. which'hasa A "diameter hole in itsfcenter (i e.-, shaped like ian'ordinary washer). The test piece has an exposed copperlead surface of 3.00Isq. cm; Of this surface area, 1';85"sq.icm.' acts as a loaded bearing, and is contacted by'a part of the cylindrical surface of a hardened'steel drill rod (14" diameter and fit long,"'and of 51-57 Rockwell hardness).

The drillrodisheldin'a special holder, and the holder-is rotated so that the surface of the drill rod-which contactsthe bearing sweeps the bearing surfaceithe'drill rod is not rotated on its own axis and the surface'of the'drill rod which contacts the bearing is not changed).

The corrosion test unit means for holding the bearing and the drill rod is a steel tubing 15" long and'l g O. D.) which is attached to a I support. A steel cup (1" long, 1 O. D. by t2" I. D.) is threaded into the steel tube, at the lower end. The cup has a diameter hol in the bottom for admitting the oil into the corrosion chamber. The copper-lead test piece fits snugly into the steel cup and the hole in the test piece fits over the hole in-the steel cup. A section of steel rod /8" in diameter and 19" long) serves as'a shaft and is positioned'by 2 bearings which are'fixedly set in the outer steel tubing, one near thetop and'one near the lower (threaded) end thereof. Several holes are drilled just above and just'below the lower bearing. The holes above the bearing facilitate cleaning the apparatus, while the holes below the bearing enable the circulation of oil through the corrosion chamber. The drill rod holder is connected to'the shaft by a self-aligning yoke' and pin coupling. This assures instantaneous and continuous alignment of the drill rod bearing member against the bearing surface atall times. A pulley is fitted to the top of the steel shaft and the shaft is connected therethrough to a power source. The shaft is rotatedat about 675R. P. M.; and the weight of the'shaft' and attached'members is about 600 grams, which is the gravitational force which represents \the'thrust on the bearing. Theair lift .5 from the air inlet pumps the oil through the chamber containing the test piece and out through the holes in the steel tubing.

The ratios of surface active metals to the volume of oil in an internal combustion test engine are nearly quantitatively duplicated in the test equipment. The temperature used is approximately that of the bearing surface. The rate of air flow per volume of oil is adjusted to the same as the average for a test engine in operation. 01 the catalytic effects, those due to soluble iron are the most important. They are empirically duplicated by the addition of a soluble iron salt. Those due to lead-bromide are duplicated by its addition.

The test was correlated with the L-4 Chevrolet test, and a slightly modified version thereof. The modified test comprised reducing the oil additions from the 4 quarts in the usual procedure to 2 quarts, by reducing the usual 1 pint-oil additions which are made at 4 hour intervals to /2 pint additions. This modification increases the severity of the test in its corrosion and detergency components, particularly in the case of border line oils.

For each test, the glass parts are cleaned by the usual chromic acid method, rinsed and dried. The metal parts are washed with chloroform and carbon disulfide and polished with No. 925 emery cloth or steel wool. A new copper-lead test piece is used for every test. The test piece is polished before use, on a surface grinder to give it a smooth finish. The test piece is weighed before and after the test on an analytical balance to evaluate the corrosion. After placing the oil and corrosion test unit in the tube, and bringing the assembly up to temperature in the thermostat, soluble catalyst is added and the air flow is started. Lead bromide catalyst is added immediately after starting the air, and timing of the test is begun.

The laboratory test conditions which were found to correlate with the Chevrolet procedure 36-hour test are shown in the following table.

Table A Temperature325 F. Oil sample107-cc. Air flow rate-70 liters/hour Time-1O hours CatalystsSteel; copper-lead bearing: 3 sq. cm. area of which 1.85 sq. cm. is a bearing surface; ferric 2-ethyl hexoate; 0.05% as FezOa' in C. P. benzene; lead bromide; 0.1% as precipitated powder. Bearing assembly:

Load grams-. 600 Speed R. P. M 675 By extending the laboratory test to 20 hours, it was found that correlation with the Chevrolet 72-hour test could be obtained.

At the close of the test period, the extent of corrosion is determinedby reweighing the corrosion test piece and determining the change 'in weight due to the test. An accurate evaluation of the lacquering properties. of an oil is obtained by a visual rating system which is applied to the outer surface of the corrosion unit steel tube and metal cup in much the same way that the piston skirt, cylinder wall, etc. of an engine are rated for varnishes. The sludge rating of the engine is-simulated by a visual rating of the insoluble materials and usedoil which are coated on the glass test tube at the conclusion of the 6 test. For both sludge and varnish rating a scale rating of A (best) to F (worst) is used.

A sufficient volume of used oil is obtained from the test for determination of the usual used oil properties, such as pentane insolubles (sludge), viscosity increase, neutralization number and optical density.

The term optical density, as used in the present disclosure, represents the standard logarithmic ratio of intensity of an incident ray falling on a transparent or translucent medium to the intensity of the transmitted ray for a sample length of one meter and light of wave length from 5100 to 5500 Angstroms.

The data in the following tables typify the results obtained in 20-hour Sohio corrosion tests on the hydrocarbon lubricating oil base stock, and the improved lubricants prepared therefrom in accordance with the invention.

Table I Lubricant Example N o A 1 B 2 C 3 Corrosion of Ou-Pb (in ngms, weight loss of).. 28.1 55.0 443. 4 63.4 40.1 1.4 Viscosity Increase (SUS) 938 535 3, 215 620 4, 070 91 Pentane Insolubles (in mgm./l0 g. of lubricant) 895 616 1, 005 378 25. 8 5. 0 Acid Number. 5. 39 3. 56 5. 1 4. 5 11. 3 1. 5 Sludge Rating.-. D- D A A- A- A+ Lacquer Rating E D A B A A Optical Density 284 65. 7 48. 2 105. 3 41 84. 4

It may be noted that the solvent extracted oil B is better than the raw oil A as far as sludge and lacquer rating are concerned, but the corrosion and viscosit increase characteristics are worse. The subsequently clay-treated solvent extracted oil C is somewhat better as to corrosion, but the viscosity increase is even worse.

The Example 1, 2 and 3 data show that the process of the invention improves the oils in almost all respects. Example 1 is superior to oil A in every respect except a slight increase in corrosion which is not beyond the objectionable point. The very great improvement in corrosion, viscosity increase and pentane insolubles characteristics of the lubricant of Example 2, as compared to oil B, is particularly noteworthy. The lubricant of Example 3 is even better, thus showing that the combination of solvent extraction, clay treatment, and then treatment with the phosphorus sulfide is most effective. The slight increase in color is not objectionable in view of the other good characteristics.

Table II Lubricant- Example No O 4 Corrosion of Ou-Pb (in mgms. weight loss of) l 33.2 8.4 1.4 Viscosity Increase 4, 070 450 145 91 731 4, 770 Pentane Insolubles (1n mgnL/lO g. of lubricant) 25.8 168.0 9.3 5.0 65.8 69.9 355.0 Acid Number 11.3 5.1 2. 3 1. 5 1. 7 2. 8 1. 57 Sludge Rating A- A+ A A+ A A- B-{ Lacquer Rating A- A- B- A B- B 0 Optical Density...w 41 87. 8 84. 9 84. 4 05. 3 78. 2 81. 6

Examples 4, 5, 1a, 6, "7, and X show the eifects of varying the amount of phosphorus sulfide. As the amount of the sulfide is increased from 0.2%, there is generally an improvement in characteristics, with a peak at about 0.4% (Example 1a), for most characteristics. At higher amounts (Example 6, and 7) the viscosity increase characteristic increases, the pentane insolubles go up, and the lacquer rating is down.

In the comparative run (Example X), using 1.0% of the phosphorus sulfide, the viscosit increase was even higher than that of the oil C, the pentane insolubles had gone up very high and the lacquer rating gone to the lowest value of the-series tested. Thus the amount of phosphorus sulfide should not be above about 0.75%.

Table III Lubricant Example No O 8 9 10 11 12 Y Corrosion of Cu-Pb (in mgms. Weight loss of) 40. l 0. 4 3. 4 5.8 6.5 19. 5 46. 4 Viscosity Increase Pentane Insolubles (in mgmJlO G. of

lubricant) 25. 8 84. 7 55.0 20 2.1 8. 6 954 Acid Number. 11.3 0.62 0.49 0.9 1. 5 1. 4 12.3 Sludge Rating A A A A A A A Lacquer Rating. A A A A A B+ B Optical Density..." 41 70. 3 60. 8 74.0 65. 3 54. 8 75. 7

The Example 8, 9 and 10 data indicate the use of P483 in the process of the invention, and show that an excellent lubricant is obtained thereby.

The Examples 11, 12 and Y data show that the treatment temperature should be desirably at least about 300 F. (Example 12) and preferably at least about 400 F. (Example 11) In a comparative run (Example Y), at 200 F., the corrosion, viscosity increase, acid number and pentane insolubles characteristics were worse than those of the oil C; thus showing that a temperature considerably below about 275 F. is not suitable.

The 36-hour L-4 Chevrolet engine test was also used in comparing the oil C with the lubricant of Example 8. In this test, new piston rings and two new copper-lead bearing inserts are installed in the motor prior to each test. The engine is a conventional Chevrolet engine with 216.5 cu. in. piston displacement and a compression ratio of 6.5 to 1. The engine is operated at 3150 R. P. M. with a load of 30 B. H. P. and at a temperature at the jacket outlet of 200 F. The lubricating oil'temperature is maintained at 265 F. for an S. A. E. 10 grade oil, and at 280 F. for oils of S. A. E. 30 to 50 grades. The fuel used contains from 2.5 to 3.0 ml. tetra-ethyl lead per gallon. Besides the weight loss of the test bearings, deposits in the power section, and properties of the used oil, sampled near the middle and also at the end of the test, are examined. The following results were obtained:

Table IV LubricantExample No C 8 Overall Rating 92. 89.00 Bearing Corrosion (mgmslbcaring half-shell)... l, 428 85. Viscosity Increase (SUS) 210 105 Pentane Insolubles (in perccnt by weight) 1.10 1.01 Acid Number 2. 4 2.05

phosphorus'sulfide, or hydrocarbon lubricating oil stock, within the broadtypes and ranges as indicated hereinbefore, comparable improved lubricants are obtained.

If desired, the improved lubricants of the invention may be used in blends together with other lubricants orlubricant agent, e. g., with soap or the like in a grease. If desired, an agent for improving the clarity ofthe oil may be included, e. g., lecithin, lauryl alcohol, and the like. If desired, an agent for preventing foaming may be included, e. g., tetra-amyl silicate, an alkyl orthocarbonate, ortho-formate or ortho-acetate, or a polyalkyl silicone oil.

In view of the foregoing disclosure, variations and modifications of the invention will be apparent to those skilled in the art, and it is intended to claim such variations and modifications broadly, except as do not come within the scope of the appended claims.

I claim:

1. A method of processing lubricating oil stock consisting essentially of hydrocarbon material to yield an oil having improved inhibition to oxidation in service, which method comprises treating said stock with an amount in the range of about 0.1 to about 0.75% by weight of a phosphorus sulfide at a temperature in the range of 275 to 450 F.

2. The method of claim 1 wherein the phosphorus sulfide is phosphorus pentasulfide.

3. The method of claim 1 wherein the stock is a raw oil.

4. The method of claim 1 wherein the stock is a solvent extracted oil.

5. The method of claim 4 wherein the stock is a clay-treated oil.

6. The method of claim 1 wherein the stock is treated with an amount of phosphorus pentasulfide in the range of about 0.3 to about 0.6% at a temperature in the range of 300 to 450 F.

'7. The method of claim 6 wherein the stock is a raw oil.

8. The method of claim 6 wherein the stock is a solvent extracted oil.

9. The method of claim 8 wherein the stock is a clay-treated oil.

10. The method of claim 8 wherein the stock is treated with about 0.4% of phosphorus pentasulfide at a temperature in the range of 350 to 400 F.

11. The method of claim 1 wherein the stock is treated with an amount in the range of about 0.15 to about 0.4% of phosphorus sesquisulfide at a temperature in the range of 300 to 450 F.

12. A lubricant prepared by the process claim 1.

13. A claim 2.

14. A claim 3.

15. A claim 4.

16. A claim 5.

17. A claim -6.

18. A claim 7.

19. A claim 8.

20. A claim 9.

21. A claim 10.

lubricant prepared by the process of lubricant prepared by the process of lubricant prepared by the process of lubricant prepared by the process of lubricant prepared by the process of lubricant prepared by the process of lubricant prepared by the process of lubricant prepared by the process of lubricant prepared by the process of REFERENCES CITED The following references are of record in the file of this patent:

Number 10 UNITED STATES PATENTS Name Date White Apr. 6, 1943 Musselman Jan. 22, 1946 Hughes Apr. 16, 1946 Noland Apr. 29, 1947 

1. A METHOD OF PROCESSING LUBRICATING OIL STOCK CONSISTING ESSENTIALLY OF HYDROCARABON MATERIAL TO YIELD AN OIL HAVING IMPROVED INHIBITION TO OXIDATION IN SERVICE, WHICH METHOD COMPRISES TREATING SAID STOCK WITH AN AMOUNT IN THE RANGE OF ABOUT 0.1 TO ABOUT 0.75% BY WEIGHT OF A PHOSPHORUS SULFIDE AT A TEMPERATURE IN THE RANGE OF 275* TO 450* C.
 12. A LUBRICANT PREPARED BY THE PROCESS OF CLAIM
 1. 